harder



United States Patent LINE-CONTACT SEALING FIXTURE Arthur J. Harder, In, Franklin Park, Ill., assignor to The Rauland Corporation, a corporation of Illinois Application April 4, 1952, Serial No. 280,693

Claims. (Cl. 118-500) This invention relates to a line-contact sealing fixture for effecting a pressure seal in a container opening or neck. The invention is useful wherever a continuous line seal is desirable, but is particularly valuable in the manufacture of cathode-ray tubes and will be described in that connection.

One of the steps in the manufacture of cathode-ray tubes for use in television receivers and similar apparatus includes the application of a layer of conductive material to the internal surface of the tube envelope; this layer is usually formed by the deposition of colloidal graphite and covers substantially the entire inner periphery of the tube from a point a short distance from the face or screen surface of the envelope to a point near the mouth or free end of the tube neck. One practical method of applying this coating comprising mounting the envelope vertically with its screen surface facing up and closing the free end of the neck with a sealing fixture that is apertured to rceive a conduit through which a coating solution may be admitted to the envelope. The envelope is then filled to the desired level with a suspension of colloidal graphite; the suspension is later drained, leaving a conductive layer of graphite deposited on the preselected portion of the envelope wall.

It is highly desirable that the coating of conductive material terminate in a clean line circumscribing the inside of the envelope neck, since irregularitiesat this point may cause electrical disturbances when the tube is placed in operation. An ordinary stopper or plug used to seal the neck during the coating operation provides a sealing contact surface of irregular contour and permits retention of liquid between the stopper and envelope wall after draining has been completed. Consequently, after the stopper has been removed a series of streaks and islands are often found at the edge-of the coating. Such islands and other irregularities are, as noted before, extremely undesirable. On the other hand, it is possible to paint the coating on the internal surface of the envelope with a brush, and a skillful operator may avoid undesirable streaks and islands at the edge of the coating. However, good commercial practice demands that any possible reduction in the skill required in production techniques be taken advantage of, for obvi'ousreasons of economy.

It is, therefore, an object or" this invention to provide a line-contact sealing fixture which avoids the above-described deficiencies inherent in thejsealing means known to. the prior art.

It is a further object of the invention to provide such a fixture which is economical to construct and simple to use.

' It is yet another object of this invention to provide a sealing fixture which may be economically and expediently maintained in operative condition.

It is a specific object of the invention to provide a fixture which permits economical coating of cathode-ray tubes and eliminates the necessity of finishing the process by hand painting. 4

Accordingly, the invention provides a line-contact seal- 4 2,731,947 Patented Jan. 24, 1956 ing fixture comprising a mounting member to which is affixed a sealing member, the sealing member including a tubular base portion having a free end constituting a sealing surface or rim and a flange portion joined to and depending inwardly from the tubular base portion. The external surfaces of the tubular portion and the flange portion join at an angle no greater than 45 degrees at the sealing rim. A piston is adjustably mounted to the mounting member coaxially with the sealing member in position to engage an internal surface on the flange portion thereof.

The features of the present invention which are believed to be novel are set forth with particularity in the appended claims. The invention itself, both as to its organization and manner of operation, together with further objects and advantages thereof, may best be understood by reference to the followng description taken in connection with the accompanying drawings, in the several figures of which like reference numerals indicate like elements, and in which:

Figure 1 is a sectional view of sealing apparatus comprising a preferred embodiment of the invention in which certain parts have been foreshortened in order to save space;

Figure 2 is an enlarged sectional view of a portion of the apparatus shown in Figure 1; and

Figure 3 is an enlarged sectional representation of another embodiment of that portion of the sealing apparatus shown in Figure 2.

The apparatus shown in Figure 1 comprises a sealing fixture, embodying the invention, installed in its operative position. A mounting member lli which forms part of the sealing fixture is supported by a base or worktable 11, the sealing portion of the fixture extending above the work-table. A sealing member 12 is vulcanized or bonded to a retaining ring 13 which is removably attached to mounting member 10 by means of a threaded joint. A hollow piston 14 is mounted internally of member 10 and is adjustably movable along the axis of sealing member 12 as indicated by arrow 15.

Piston M is provided with a guide and support collar 21' which extends radially from the piston, the lower surface of collar 2i bearing against a washer 16. Washer 16 rests upon a sprocket wheel 17 which is rotatably and adjustably fixed to mounting member 10 by a threaded connection 21. A pair of locating screws 18 are threaded into mounting member it); each of the locating screws is provided with a sleeve 19 encompassing that portion of the screw extending from the mounting member. The sleeves 19 are received in a pair of recesses 22 formed in collar 20. Access to the central opening in hollow piston 14 is provided by an intake conduit 24 which projects radially from the lower portion of the piston. An air tube 25 is mounted coaxially within hollow piston 14 and is of sutlicient length to protrude both above and below the extremities of the piston; the air tube is sealed to the lower portion of piston 14 by a doughnut-shaped rubber sealing flange 26', which effects a seal without restricting movement of the tube.

As more clearly represented in the enlarged half-section view=of Figure 2, sealing member 12 comprises a tubular base portion 26, the upperextremity of which constitutes a sealing surface or rim 27; member 12 also includes a reentrant flange portion 28 which is joined to and depends inwardly from sealing surface 27. The external surface 29 of the reentrant flange portionforms an angle of approximately 35 dcgrees.with the external surface 3% of tubular portion 25. The trailing edge of the reentrant flange portion is perpendicular to the axis of sealing member 12, and forms an internal bearing surface 31. Moreover, the reentrant flange is relieved with respect to tubularbase portion 26 so that its internal surface 33, which joins the internal surface 34 of base portion 26, forms therewith a smaller angle than that defined by the external surfaces 29, 30 of these portions.

In this particular embodiment the angle formed by surfaces 33, 34 is approximately 19 degrees. The angular relation is such that even though the reentrant portion is tapered, its wall thickness at any point exceeds the wall thickness of tubular portion 26, particularly in the vicinity of the meeting plane of the tubular and reentrant portions. The upper extremity of piston 14 is shown in engaging contact with bearing surface 31 of flange portion 28 and it carries a perforated guide member 35 which positions air tube within the piston but does not seal off the central opening of the piston. As more clearly indicated in Figure l, a cathode-ray tube onvclope 36 is supported above the sealing fixture, the neck 37 of envelope 36 being established in encompassing relationship to scaling member 12. The central portion of envelope 36 has been cut away in order tosave space; the continuation of envelope 36 above the broken section is shown as terminating in a face plate or screen surface 38. Envelope 36 may be supported by a suitable mounting structure (not shown).

Insofar as the normal process of coating a cathode-ray tube is concerned, the function of the sealing fixture will be apparent to those versed in the art and hence a detailed description thereof is unnecessary. Briefly, at the start of the coating operation cathode-ray tube envelope 36 is installed over the sealing fixture in the position indicated in Figure l, with neck 37 encompassing sealing member 12. Neck 3'7 and sealing member 12 are then effectively sealed together in a manner to be described more completely hereinafter. Air tube 25 is elevated within envelope 36 to the position shown, in which the upper extremity of the tube approaches screen surface 38. A colloidal graphite suspension is pumped into envelope 36 through intake conduit 24 and the internal opening of hollow piston 14; the air in the envelope is permitted to escape through air tube 25. After envelope 36 has been filled to the desired point near the screen surface, as indicated by line B, the graphite suspension is drained, leaving a conductive coating deposited on the internal surface of envelop 36 from line B to the point of sealing between sealing member 12 and neck 37. Envelope 36 is then released and removed from the sealing fixture.

In employing the invention to seal neck 37, after envelope 36 has been installed in the position indicated, sprocket wheel 17 is rotated to displace piston 14 relative to member 10 in the direction indicated by arrow 15. This movement, which is provided for by threaded connection 21, is transmitted to piston 14 by washer 16 and collar 29 and guided by locating screws 18, and results in the application of pressure against bearing surface 31 through its contact with the upper extremity of piston 14. This causes flange portion 28 to pivot about a fulcrum C in the manner indicated in Figure 2. As a re sult, sealing member 12 is forced into the configuration represented by the dotted lines in Figure 2, with sealing surface 27 in contact with neck 37 at a point D. This deformation of sealing member 12 results in a continuous line-contact with external surface 29 of flange portion 28 extending away from the line of contact at a very sharp angle. The sharp slope of surface 29 with respect to neck 37 obviates any possible tendency for the collection of the graphite suspension at contact plane D when the suspension is drained from envelope 36, and thus precludes the formation of streaks and islands in the coating termination line.

Figure 3 represents another embodiment of the invention in a view corresponding to that of Figure 2 with sealing member 12 again shown in an unstressed condition. Piston 14 is in contact with bearing surface 31, but no force is currently applied thereto. In this embodiment, external surfaces 29 and 30 join at sealing surface 27 to form an angle of 45 degrees; bearing surface 31 is not relieved as it was in the previous embodiment, but extends to join internal surface 34 of base portion 26 at an angle of 90 degrees.

When force is applied to bearing surface 31 by piston 14 in the direction indicated by arrow 15, flange portion 28 pivots with respect to fulcrum C on base portion 26 and tends to compress and deform. The combination of pivotal movement and deformation of the flange portion alters the configuration of sealing member 1.2 to conform to that indicated by the dotted outline. Thus, sealing surface 27 is forced into a continuous line-contact with envelope neck 37 at the point D. This embodiment of the invention functions in much the same mannor as that shown in Figures 1 and 2; however, it exhibits a slightly greater tendency to collect liquid material at contact point D when envelope 36 is drained, since internal flange surface 29 does not form as acute an angle with wall 37 as in the first described structure.

The invention therefore provides a fixture for effectively sealing the neck of a container or envelope in a clean and continuous line. The fixture will withstand considerable pressure, since the fluid pressure built up within the neck of the envelope tends to force sealing surface 27 into more positive contact with neck 37. Maintenance of the fixture is facilitated by use of the removable retaining ring 13 as a means for mounting sealing member 12 on member 10; when individual sealing members become worn, replacement may be simply and expeditiously effected. The fixture is composed of parts which are relatively simple in form and therefore easy and economical to manufacture, and use of the fixture requires no precise skill or extensive knowledge on the part of the operator. The provision of an acute angle between the external surfaces 29, 311 of tubular base portion 36 and flange portion 28 of the sealing member prevents accumulation of liquid material at the line of contact between sealing surface 27 and neck 37 after drainage and avoids this source of irregularities when the fixture is used in a coating process, thereby eliminating any necessity for finishing the coating by hand painting procedures.

While particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from this invention in its broader aspects, and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of this invention.

I claim:

1. A line-contact sealing fixture comprising: a mounting member; a sealing member aflixed to said mounting member, said sealing member including a tubular base portion having a free end constituting a sealing rim and further including a flange portion joined to and depending inwardly from said tubular base portion, the external surfaces of said tubular portion and said flange portion joining at an angle no greater than 45 degrees at said sealing rim; and a piston adiustably mounted in coaxial relation with said sealing member in position to engage an internal surface on said flange portion thereof.

2. A line-contact sealing fixture comprising: a mounting member; a sealing member aflixed to said mounting member, said sealing member including a tubular base portion having a free end constituting a sealing rim and further including a flange portion joined to and depending inwardly from said tubular base portion, said tubular portion and said flange portion having external surfaces joining at a first angle no greater than 45 degrees at said sealing rim and further having internal surfaces joining at an acute angle smaller than said first angle; and a piston adjustably mounted in coaxial relation with said sealing member in position to engage an internal bearing surface on said flange portion thereof.

3. A line-contact sealing fixture comprising: a mounting member; a sealing member aifixed to said mounting member, said sealing membezincluding a tubular base portion having a free end constituting a sealing rim and further including a flange portion joined to and depending inwardly from said tubular base portion, the wall thickness of said flange portion being greater than the wall thickness of said tubular portion at least in the vicinity of their meeting plane and the external surfaces of said portions defining an angle no greater than 45 degrees; and a piston adjustably mounted in coaxial relation with said sealing member in position to engage an internal surface on said flange portion thereof.

4. A line-contact sealing fixture comprising: a mounting member; a sealing member coaxially and removably fixed to said mounting member, said sealing member including a tubular base portion having a free end constituting a sealing rim and further including a flange portion joined to and depending inwardly from said tubular base portion, the external surfaces of said tubular portion and said flange portion joining at an angle no greater than 45 degrees at said sealing rim; and a hollow piston adjustably mounted on said mounting member coaxially with said sealing member in position to engage an internal surface on said flange portion thereof and apply force to said flange portion parallel to the com mon axis of said moutning member and said sealing member. 1

5. A line-contact sealing fixture comprising: a mount ing member; a sealing member affixed to said mounting member, said sealing member including a tubular base portion having a free end constituting a sealing rim and further including a flange portion joined to and depending inwardly from said tubular base portion, the external surfaces of said portions joinnig at a first angle no greater than 45 degrees at said sealing rim and the internal surfaces of said portions joining at an angle of approximately 90 degrees; and a hollow piston adjustably mounted on said mounting member coaxially with said sealing member in position to engage an internal surface 5 of said flange portion thereof.

References Cited in the file of this patent UNITED STATES PATENTS 2,077,378 Deren Apr. 20, 1937 2,123,706 Biggs July 12, 1938 2,328,203 Duggan Aug. 31, 1943 2,359,974 Duggan Oct. 10, 1944 2,464,764 Myers Mar. 15, 1949 2,476,722 Gelardin July 19, 1949 2,569,852 Green Oct. 2, 1951 2,589,054 Conway et al. Mar. 11, 1952 

